IVs are "Individual Values" and are hidden points for each stat (HP, Attack etc) that are random for each pokemon. They can be from 0 to 31, and are added gradually up to level 100 (i.e. a pokemon with 20 IVs in Attack will have 20 higher attack at level 100 than if it had 0 IVs).
EVs are "Effort Values" which are extra points you get by battling different pokemon. See http://pokemondb.net/ev for a detailed description of EVs.
You cannot control what IVs your pokemon has, they are fixed from when the pokemon first appears to you. But you can control their stats quite a lot using EVs.